This invention relates to a ditcher of the type used to excavate pipeline trenches and the like.
A conventional ditcher generally comprises a carrier, usually a crawler tractor, carrying a rotatable digging wheel at its rear. More particularly, the carrier supports an upstanding, rigid suspension frame. This suspension frame includes one or two substantially vertical beams at its rear end. Each vertical beam carries a slide guide. The digging wheel is held in a rigid wheel frame, which is generally rectangular in shape and extends around the wheel. The front end of this wheel frame is pivotally attached to a slide member. In turn, the slide member is mounted on the beam slide guide and can slide up and down thereon to alter the elevation of the wheel. A substantially vertical hydraulic cylinder is suspended from the upper end of the suspension frame and attached at its lower end to the slide member. Contraction and expansion of this cylinder moves the wheel frame between the elevated travelling position and the lowered digging position. A cable is attached to the rear end of the wheel frame. It extends over a sheave, carried by the suspension frame, to a drum on the carrier. This cable functions to suspend the wheel frame horizontally when the ditcher is digging a trench. It also serves to rotate the wheel frame upwardly, about its front pivot connection, to the elevated travelling position. The tractor is equipped with a motor, and suitable hydraulic systems and drives for operating the digging wheel and actuating the lifting cylinders. It will be noted that the conventional ditcher in use today relies on the sheer weight of the digging wheel to obtain penetration into the soil -- although it has been suggested by others that the cable may be replaced with a hydraulic cylinder to force the wheel down (see U.S. Pat. Nos. 3226856 and 3510970).
At the present time there is a need for a ditcher which can operate in the Arctic to excavate trenches for the laying of large-diameter pipelines.
The Arctic ditcher is required to excavate a uniquely large trench through extremely hard material. With this in mind, it is an object of the invention to provide a ditcher which is powered by twin enginers -- one of which drives the digging wheel only while the other engine drives the remaining hydraulic components. In this manner, the power available to the digging wheel is not diminished due to periodic heavy load conditions affecting other parts of the machine.
The ditcher is called on to operate under extremely severe weather conditions. Temperatures below -60.degree.F are not uncommon. Under these conditions, the frequency of mechanical breakdown is enormously increased. It is therefore another object of this invention to incorporate an emergency cross-over system into the hydraulic circuitry of the machine so that, in the event that one engine breaks down, the other engine can take over sufficient functions to enable the ditcher to lift its wheel, move off the right of way, and return to the base camp for repair, or continue operating at a reduced production rate.